Exercise

Exercise is the act of actually using the right that an options contract gives you, instead of just trading the contract itself. An option is a piece of paper (electronic these days) that grants a right, not an obligation, to buy or sell some underlying stock at a set price. Most of the time traders never exercise; they just buy or sell the option itself for a profit or loss. Exercise is when someone actually invokes that right.

If you own a call option, exercising means you use your right to buy the underlying stock at the strike price (the price locked into the contract), no matter where the stock is actually trading. If you own a put option, exercising means you use your right to sell the underlying stock at the strike price. In either case, exercising converts the option into an actual stock position at that fixed price.

The person on the other side of your contract is called the seller, or writer. When you exercise, the writer is "assigned," meaning they are obligated to fulfill their side: deliver stock if you exercised a call, or buy stock if you exercised a put. Whether an option is worth exercising depends mostly on whether it's in the money, meaning the strike price is more favorable than the current market price.

The nuance that trips people up is that exercise is not the same as the option's value changing hands like a normal trade. Selling an option you own closes your position and locks in a profit or loss directly. Exercising instead creates a brand new stock position at the strike price, which then has its own separate risk. Many beginners exercise a profitable option expecting a payout, and are surprised to find themselves holding shares instead, with all the capital and risk that involves. There are also mechanical details, like how and when exercise can happen and what happens automatically at expiration, that vary by contract type and broker, and are worth confirming rather than assuming.